Abstract
•People with diabetes and a low (inadequate) plasma vitamin C concentration may show inappropriate renal leak of vitamin C.•Renal leak of vitamin C is more likely to be seen in type 2 diabetes compared to type 1 diabetes.•Quantitively, this inappropriate urinary loss of vitamin C is modest and equates to around 5–10 mg of vitamin C a day.•Even a modest loss of vitamin C may be of clinical significance in patients with very low plasma vitamin C concentrations.
Hypovitaminosis C has negative health consequences. People with diabetes and hypovitaminosis C may fail to conserve vitamin C in the urine, thereby displaying evidence of inappropriate renal leak of vitamin C. This study describes the relationship between plasma and urinary vitamin C in diabetes, with a focus on the clinical characteristics of participants with renal leak.
Retrospective analysis of paired, non-fasting plasma and urine vitamin C, and also clinical characteristics, from participants with either type 1 or type 2 diabetes, recruited from a secondary care diabetes clinic. Plasma vitamin C thresholds for renal leak have been defined previously as 38.1 µmol/L for men and 43.2 µmol/L for women.
Statistically significant differences in clinical characteristics were seen between those with; i) renal leak (N = 77) and; ii) hypovitaminosis C but no renal leak (N = 13) and; iii) normal plasma vitamin C levels (n = 34). Compared to participants with adequate plasma vitamin C levels, participants with renal leak tended to have type 2 (rather than type 1) diabetes, a lower eGFR and a higher HbA1c.
In the diabetes population studied, renal leak of vitamin C was common. In some participants, it may have contributed to hypovitaminosis C.